[Color] Boundary Detection Benchmark: Algorithm "Color Gradient"

This algorithm uses local color gradients to detect boundaries. The A
and B gradient channels (from CIELAB) are combined with a logistic to
model the posterior probability of a boundary. The color gradient is
computed as the chi-squared difference in the distribution of pixel
chrominance values in two half discs centered at a pixel and divided
in half at the putative boundary orientation. See our NIPS and PAMI
papers in the Grouping
area of the Berkeley Vision
Group web pages for additional details.